U.S. patent application number 12/638379 was filed with the patent office on 2010-06-24 for braking circuit master cylinder lip seal.
This patent application is currently assigned to ROBERT BOSCH GMBH. Invention is credited to Antony Auguste, Olivier Bernadat, Francois Gaffe, Laurent Lhuillier.
Application Number | 20100154407 12/638379 |
Document ID | / |
Family ID | 41203752 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100154407 |
Kind Code |
A1 |
Bernadat; Olivier ; et
al. |
June 24, 2010 |
BRAKING CIRCUIT MASTER CYLINDER LIP SEAL
Abstract
Master cylinder of a hydraulic braking circuit, particularly for
a motor vehicle, comprising a piston (2) sliding axially in a body
(4) comprising an annular lip seal (51) produced by molding, and
comprising an internal, dynamic sealing lip (14) surrounding the
piston and connected by a curved surface (36) to a planar rear face
(30) comprising radial passages which are defined by blocks formed
as projections on the rear face of the seal, these blocks being
separated from the curved surface (36).
Inventors: |
Bernadat; Olivier; (Le
Perreux, FR) ; Gaffe; Francois; (Bondy, FR) ;
Lhuillier; Laurent; (Le Blanc Mesnil, FR) ; Auguste;
Antony; (Villier sur Marne, FR) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
100 EAST WISCONSIN AVENUE
MILWAUKEE
WI
53202
US
|
Assignee: |
ROBERT BOSCH GMBH
Stuttgart
DE
|
Family ID: |
41203752 |
Appl. No.: |
12/638379 |
Filed: |
December 15, 2009 |
Current U.S.
Class: |
60/533 ;
277/549 |
Current CPC
Class: |
B60T 11/236
20130101 |
Class at
Publication: |
60/533 ;
277/549 |
International
Class: |
B60T 11/16 20060101
B60T011/16; F16J 15/32 20060101 F16J015/32 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2008 |
FR |
0807183 |
Claims
1. Master cylinder of a hydraulic braking circuit, comprising a
piston (2) sliding axially in a body (4) comprising an annular lip
seal (51), this seal comprising an internal, dynamic sealing, lip
(14) surrounding the piston and connected by a curved surface (36)
to a planar rear face (30) comprising grooves (34) and pressing
against a transverse rear surface (32) of the seal housing,
characterized in that the grooves (34) of the rear face of the seal
are defined by blocks formed as projections on the rear face of the
seal, these blocks being separated from the curved convex surface
(36) for connection to the internal lip (14) of the seal, in that
the annular seal (51) is produced in a mold the manufacture of
which involves in succession a turning operation to create the
internal lip (14), the annular ring (52) and the curved surface
(36), and an operation of EDM machining to cut cavities in the mold
corresponding to the blocks of the seal and in that the annular
ring (52) is radially aligned with the bottom of the grooves
(34).
2. Master cylinder according to claim 1, characterized in that the
annular seal (51) is produced in a mold the manufacture of which
involves in succession a turning operation to create the internal
lip (14), the annular ring (52) and the curved surface (36), and an
operation of EDM machining to cut cavities in the mold
corresponding to the blocks of the seal.
3. Annular lip seal (51) of a master cylinder of the type described
in claim 1, this seal comprising an internal, dynamic sealing, lip
(14) connected by a curved surface (36) to a planar rear face (30)
comprising radial passages, characterized in that the radial
passages are defined by blocks formed as projections on the rear
face of the seal, these blocks being separated from the curved
connecting surface (36).
4. Seal according to claim 3, characterized in that it is produced
by molding.
5. Annular lip seal (51) of a master cylinder of the type described
in claim 2, this seal comprising an internal, dynamic sealing, lip
(14) connected by a curved surface (36) to a planar rear face (30)
comprising radial passages, characterized in that the radial
passages are defined by blocks formed as projections on the rear
face of the seal, these blocks being separated from the curved
connecting surface (36).
6. Seal according to claim 5, characterized in that it is produced
by molding.
7. Master cylinder of a hydraulic braking circuit for a motor
vehicle, comprising a piston (2) sliding axially in a body (4)
comprising an annular lip seal (51), this seal comprising an
internal, dynamic sealing, lip (14) surrounding the piston and
connected by a curved surface (36) to a planar rear face (30)
comprising grooves (34) and pressing against a transverse rear
surface (32) of the seal housing, characterized in that the grooves
(34) of the rear face of the seal are defined by blocks formed as
projections on the rear face of the seal, these blocks being
separated from the curved convex surface (36) for connection to the
internal lip (14) of the seal, in that the annular seal (51) is
produced in a mold the manufacture of which involves in succession
a turning operation to create the internal lip (14), the annular
ring (52) and the curved surface (36), and an operation of EDM
machining to cut cavities in the mold corresponding to the blocks
of the seal and in that the annular ring (52) is radially aligned
with the bottom of the grooves (34).
8. Master cylinder according to claim 7, characterized in that the
annular seal (51) is produced in a mold the manufacture of which
involves in succession a turning operation to create the internal
lip (14), the annular ring (52) and the curved surface (36), and an
operation of EDM machining to cut cavities in the mold
corresponding to the blocks of the seal.
9. Annular lip seal (51) of a master cylinder of the type described
in claim 7, this seal comprising an internal, dynamic sealing, lip
(14) connected by a curved surface (36) to a planar rear face (30)
comprising radial passages, characterized in that the radial
passages are defined by blocks formed as projections on the rear
face of the seal, these blocks being separated from the curved
connecting surface (36).
10. Seal according to claim 9, characterized in that it is produced
by molding.
11. Annular lip seal (51) of a master cylinder of the type
described in claim 8, this seal comprising an internal, dynamic
sealing, lip (14) connected by a curved surface (36) to a planar
rear face (30) comprising radial passages, characterized in that
the radial passages are defined by blocks formed as projections on
the rear face of the seal, these blocks being separated from the
curved connecting surface (36).
12. Seal according to claim 11, characterized in that it is
produced by molding.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a master cylinder of a
braking circuit, particularly for a motor vehicle.
[0002] Motor vehicles comprise a brake control generally comprising
a brake pedal acting on a master cylinder, to transmit, via a
hydraulic circuit, a fluid pressure to receivers that brake the
various wheels.
[0003] The master cylinder comprises a piston sliding axially in a
body comprising a lip seal which presses against the piston, in
order to separate a rear volume containing a reserve of liquid at
atmospheric pressure from a front volume comprising a chamber
pressurized by the displacement of this piston.
[0004] A master cylinder of this type, described in document U.S.
Pat. No. 6,272,858 B1, is equipped with a circular seal with two
lips. The internal lip of the seal surrounds the piston providing
dynamic sealing and, when the piston is at rest in a rear position,
enters a piston groove which has a shallow depth and gently
inclined side walls.
[0005] In this piston rest position, a radial drilling formed in
the piston opens into the groove behind the internal lip of the
seal, to place the pressure chamber in communication with the
reserve of liquid and, if necessary, readjust the volume of the
hydraulic circuit.
[0006] The lip seal is wedged axially in an annular housing of the
body around the piston and comprises an external lip which presses
against an external cylindrical wall of this housing, to provide
static sealing between the pressure chamber and the rear
volume.
[0007] The seal additionally comprises a planar rear face which
presses against a planar transverse rear face of the annular
housing, to wedge the seal axially in the housing.
[0008] Motor vehicles may comprise driving aid systems which brake
some of the wheels of the vehicle, for example to stabilize the
course followed by the vehicle, in the case of ESP systems.
[0009] In such cases, the system may quickly call for substantial
amounts of liquid in the brake circuit, which liquid is drawn
through the master cylinder to be supplied to the wheel brakes,
from the reserve of brake fluid. The fluid has then quickly to pass
via the lips of the annular seal, which lift because of the
depression pulled downstream.
[0010] In an known arrangement, the rear face of the annular seal
comprises radial grooves which extend over the entire height of the
seal, so as to allow liquid to pass radially outwards, between the
annular seal and the planar rear face of the housing of the
body.
[0011] When there is a demand for fluid in the brake circuit, the
liquid follows a path along the radial grooves to reach the
external lip, and feeds into the braking circuit via this path.
[0012] In the case of an annular seal that has been produced by
molding, one known method of manufacturing the mold is to use EDM
machining to machine that surface of the mold that corresponds to
the rear face of the annular seal, comprising the bearing surfaces
and the grooves, using a one-piece electrode.
[0013] A chief disadvantage with this method, given the spread on
manufacturing dimensions, is that it is possible that the electrode
may not be positioned precisely relative to those parts of the mold
that have been produced beforehand by turning, and this may give
rise to leaks in the annular seal at the lines where the surfaces
created by turning meet those created by EDM, when such lines are
on a dynamic sealing surface.
SUMMARY OF THE INVENTION
[0014] It a particular object of the present invention to avoid
these disadvantages of the prior art and to bring to the creation
of a master cylinder lip seal a solution that is simple and
effective and guarantees good sealing.
[0015] To this end, the present invention proposes a master
cylinder of a hydraulic braking circuit, particularly for a motor
vehicle, comprising a piston sliding axially in a body comprising
an annular lip seal separating a rear volume containing a reserve
of liquid from a front volume comprising a pressurizing chamber,
this seal comprising an internal, dynamic sealing, lip surrounding
the piston and connected by a curved surface to a planar rear face
comprising radial passages and pressing against a transverse rear
surface of the seal housing, characterized in that the radial
passages are defined by blocks formed as projections on the rear
face of the seal, these blocks being separated from the curved
surface for connection to the internal lip.
[0016] One essential advantage of the annular seal according to the
invention is that the EDM electrode used to form, in the mold,
cavities that correspond to the aforementioned blocks of the rear
face of the seal, can be slightly off-centered with respect to the
dynamic sealing surfaces, without any detrimental effect on these
surfaces.
[0017] According to another feature of the invention, the annular
seal comprises on its rear face a planar transverse surface forming
a continuous annular ring situated radially between the blocks and
the curved surface, these blocks projecting axially rearward with
respect to this planar annular ring.
[0018] Advantageously, the annular ring is radially aligned with
the bottom of the grooves.
[0019] The invention also proposes an annular lip seal for a master
cylinder of the type described hereinabove, this seal comprising an
internal, dynamic sealing, lip connected by a curved surface to a
planar rear face comprising radial passages, characterized in that
the radial passages are defined by blocks formed as projections on
the rear face of the seal, these blocks being separated from the
curved surface for connection to the internal lip of the seal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention will be better understood and other features
and advantages will become more clearly apparent from studying the
following description given by way of example, and by referring to
the attached drawings in which:
[0021] FIG. 1 is a perspective view of an annular seal according to
the prior art;
[0022] FIG. 2 is an axial half section of this annular seal on the
plane II-II;
[0023] FIG. 3 is an enlarged axial half section of part of this
annular seal pressing against the piston of a master cylinder;
[0024] FIG. 4 is a perspective view of an annular seal according to
the invention;
[0025] FIG. 5 is an axial half section of this annular seal on the
plane V-V;
[0026] FIG. 6 is an enlarged axial half section of part of this
annular seal pressing against the piston of a master cylinder.
DETAILED DESCRIPTION
[0027] FIGS. 1 to 3 depict a known annular seal 1 surrounding a
piston 2 sliding axially in a body 4 of a brake master
cylinder.
[0028] The annular seal 1 positioned in an annular housing of the
body 4, comprises an external lip 10 the end of which presses
radially against an exterior cylindrical wall of this housing, to
provide static sealing, and an internal lip 14 the end of which
presses radially against the exterior surface of the piston 2 to
provide dynamic sealing as this piston slides.
[0029] The annular seal 1 may also comprise an axial lip 12 which
is radially intermediate between the external 10 and internal 14
lips, and the end of which presses against a substantially radial
front face of the annular housing in order to wedge this seal
axially between the two, front and rear, faces of the housing.
[0030] The annular seal 1 comprises an annular and substantially
planar rear face 30 which presses against a planar transverse
surface 32 situated axially to the rear of the housing.
[0031] The rear face 30 comprises a series of radial grooves 34
distributed at even angular spacings and extending over the entire
height of the seal, forming as many radial passages allowing liquid
to flow radially outwards between the rear face 30 of the annular
seal 1 and the transverse rear surface 32 of the housing
accommodating this seal.
[0032] The radial rear face 30 of the seal is connected to the
lower surface of the internal lip 14 by a convex curved surface
36.
[0033] The mold corresponding to this seal is manufactured first of
all using turning operations to finish all the circular surfaces,
then using an EDM operation using an electrode, to form the
surfaces corresponding to the rear face 30 of the annular seal
[0034] One risk, illustrated in FIG. 3, is that given the
manufacturing tolerances, the positioning of the electrode will not
be perfectly concentric with the surfaces created by turning, and
that this may locally cause the surface 36 to be offset radially
toward the axis, with respect to the turned surfaces such as the
internal lip 14.
[0035] If this happens, the point 38 of connection between the
radial grooves 34 and the internal lip 14 may fail to come into
contact with the piston 2, thus risking leakage when the braking
circuit is pressurized.
[0036] FIGS. 4 to 6 depict a seal 51 according to the invention,
which comprises an external lip 10, an internal lip 14 and an axial
lip 12 like the known seal of FIGS. 1 to 3.
[0037] The rear face 30 of the annular seal 51 comprises a planar
annular first surface comprising the bottoms of evenly distributed
radial grooves 34, and a transverse continuous ring 52 situated
radially toward the center of this rear face and which is connected
to the lip 14 by a convex curved surface 36.
[0038] The rear face additionally comprises blocks separated from
the curved surface 36, which projects axially rearward to delimit
the grooves 34 between them.
[0039] The mold corresponding to this seal is manufactured as
follows. First of all, turning is used to produce the various
circular parts, notably the internal lip 14, the planar face
comprising the transverse ring 52 and the bottom of the radial
grooves 34, and the connecting surface 36 that joins them
together.
[0040] Next, an EDM operation using an electrode is used to cut
from the mold the cavities that will form the rear bearing blocks
of the annular seal 51.
[0041] In this way, by separating the blocks from the connecting
surface 36, and even with imperfect concentricity of the electrode
used to cut the cavities in the mold, there is no risk of creating
interference with the surface 36 and of forming a discontinuity at
this surface. The continuity of the connecting surface 36 and of
its pressing against the sliding piston 2 is assured, ensuring a
good dynamic seal against this piston.
[0042] In addition, the mold is easier to manufacture and can be
produced more simply with wider tolerances, which is more
economical.
* * * * *